I use the Empirical Audio Offramp to convert USB to SPDIF.
Cerrot, I think it's a meaningful upgrade from the Benchmark. It's not as good as the Berkeley (which I have only auditioned in other systems) but I don't have an opinion on whether the Berkeley is worth the price difference. However, if you are mainly doing computer audio and you are planning to do USB or Firewire, I would probably skip both of these DACs and go with something that is optimized for those interfaces, such as the Ayre ,Weiss, Wavelength, Sonic Studio or Metric Halo products.
Cerrot, I think it's a meaningful upgrade from the Benchmark. It's not as good as the Berkeley (which I have only auditioned in other systems) but I don't have an opinion on whether the Berkeley is worth the price difference. However, if you are mainly doing computer audio and you are planning to do USB or Firewire, I would probably skip both of these DACs and go with something that is optimized for those interfaces, such as the Ayre ,Weiss, Wavelength, Sonic Studio or Metric Halo products.

